This invention relates to production of synthetic diamond structures, particularly those which are non-planar and, more particularly, to an apparatus and method for producing non-planar diamond structures such as curved windows or free-standing domes.
Diamond has a number of properties which make it attractive for use as window material, free-standing domes, or other non-planar structures for various applications. Curved windows and domes are often used to separate a delicate sensor and/or transmitter from an outside environment. Among these properties are extreme hardness and excellent transmissivity of certain radiation. Diamond is also substantially inert, a good heat conductor, thermally stable, and an electrical insulator. However, natural diamond is prohibitively expensive for applications which require any substantial size and is difficult to form into certain shapes.
In recent years, a number of techniques have been developed for depositing synthetic diamond on surfaces of various shapes to obtain a diamond film or coating on tool surfaces and devices. These techniques include so-called high-pressure high-temperature ("HPHT") methods and chemical vapor deposition ("CVD") methods. The CVD methods include plasma deposition techniques wherein, for example, plasmas of a hydrocarbon and hydrogen are obtained using microwave energy or electrical arcing. The resultant plasma can be focused and accelerated toward a substrate using focusing and accelerating magnets. Examples of the general types of microwave plasma deposition systems that can be adapted for deposition of synthetic diamond are disclosed in U.S. Pat. Nos. 4,507,588, 4,585,668, 4,630,566 and 4,691,662. Examples of the general types of plasma jet deposition systems that can be adapted for deposition of synthetic diamond are disclosed in U.S. Pat. Nos. 4,471,003 and 4,487,162.
Although synthetic diamond has been successively deposited on tool and device surfaces for various purposes, to applicant's knowledge there are few, if any, commercially viable techniques for producing non-planar free standing diamond structures for use as windows, domes and other precisely shaped contoured structures for the types of applications wherein the above-mentioned properties of diamond are beneficial. In addition to the difficulty of obtaining a uniform thickness and quality of synthetic diamond, the production of an ultimately free-standing diamond structure poses a number of fabrication problems. It is among the objects of the present invention to provide a practical method and apparatus for producing such structures.